如何正确关闭java ExecutorService [英] How to properly shutdown java ExecutorService

问题描述

我有一个简单的java ExecutorService ，它运行一些任务对象（实现 Callable ）。

I have a simple java ExecutorService that runs some task objects (implements Callable).

ExecutorService exec = Executors.newSingleThreadExecutor();
List<CallableTask> tasks = new ArrayList<>();
// ... create some tasks
for (CallableTask task : tasks) {
 Future future = exec.submit(task);
 result = (String) future.get(timeout, TimeUnit.SECONDS);
 // TASKS load some classes and invoke their methods (they may create additional threads)
 // ... catch interruptions and timeouts
}
exec.shutdownNow();

完成所有任务（DONE或TIMEOUT-ed）后，我尝试关闭执行程序，但是它不会停止： exec.isTerminated（）= FALSE。
我怀疑某些被计时的任务没有被正确终止。

After all tasks are finished (either DONE or TIMEOUT-ed), I try to shutdown the executor, but it wont stop: exec.isTerminated() = FALSE. I suspect that some tasks that are timeouted are not properly terminated.

是的，我知道遗嘱执行人的关闭并不能保证任何事情：

And yes, I know that executor's shutdown is not guaranteing anything:

除了最好之外没有任何保证 - 努力尝试停止
处理主动执行任务。例如，典型的
实现将通过{@link Thread＃interrupt}取消，因此任何无法响应中断的
任务可能永远不会终止。

There are no guarantees beyond best-effort attempts to stop processing actively executing tasks. For example, typical implementations will cancel via {@link Thread#interrupt}, so any task that fails to respond to interrupts may never terminate.

我的问题是，有没有办法确保这些（任务）线程终止？
我提出的最佳解决方案是在程序结束时调用 System.exit（），但这很简单。

My question is, is there a way to ensure those (task) threads will terminate? The best solution I came up with, is to call the System.exit() at the end of my program, but that is plain silly.

推荐答案

来自 ExecutorService ：

 void shutdownAndAwaitTermination(ExecutorService pool) {
   pool.shutdown(); // Disable new tasks from being submitted
   try {
     // Wait a while for existing tasks to terminate
     if (!pool.awaitTermination(60, TimeUnit.SECONDS)) {
       pool.shutdownNow(); // Cancel currently executing tasks
       // Wait a while for tasks to respond to being cancelled
       if (!pool.awaitTermination(60, TimeUnit.SECONDS))
           System.err.println("Pool did not terminate");
     }
   } catch (InterruptedException ie) {
     // (Re-)Cancel if current thread also interrupted
     pool.shutdownNow();
     // Preserve interrupt status
     Thread.currentThread().interrupt();
   }

如果你的游泳池花了更多时间关机，你可以改变

If your pool is taking more time to shutdown, you can change

1f (!pool.awaitTermination(60, TimeUnit.SECONDS))

到

while (!pool.awaitTermination(60, TimeUnit.SECONDS))

---

关闭关闭的简短摘要方法

shutdown（） ：

有序启动关闭，其中先前提交的任务被执行，但不会接受任何新任务。

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted.

shutdownNow（） ：

尝试停止所有activel执行任务，停止等待任务的处理，并返回等待执行的任务列表。

Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.

awaitTermination（long timeout，TimeUnit unit）抛出InterruptedException ：

阻止所有任务完成执行在关闭请求之后，或发生超时，或当前线程被中断，以先发生者为准。

Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first.

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